https://insu.hal.science/insu-00419380Rogister, YvesYvesRogisterIPGS - Institut de physique du globe de Strasbourg - UNISTRA - Université de Strasbourg - INSU - CNRS - Institut national des sciences de l'Univers - CNRS - Centre National de la Recherche ScientifiqueValette, BernardBernardValetteLGIT - Laboratoire de Géophysique Interne et Tectonophysique - OSUG - Observatoire des Sciences de l'Univers de Grenoble - UJF - Université Joseph Fourier - Grenoble 1 - Grenoble INP - Institut polytechnique de Grenoble - Grenoble Institute of Technology - INSU - CNRS - Institut national des sciences de l'Univers - IRSTEA - Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture - USMB [Université de Savoie] [Université de Chambéry] - Université Savoie Mont Blanc - CNRS - Centre National de la Recherche Scientifique - LCPC - Laboratoire Central des Ponts et Chaussées - CNRS - Centre National de la Recherche ScientifiqueInfluence of liquid core dynamics on rotational modesHAL CCSD2009[SDU.STU.GP] Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph][PHYS.PHYS.PHYS-GEO-PH] Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph][SDE.MCG] Environmental Sciences/Global ChangesTalour, Pascale2021-03-12 10:11:522023-05-01 03:48:202021-03-12 10:12:24enJournal articleshttps://insu.hal.science/insu-00419380/document10.1111/j.1365-246X.2008.03996.xapplication/pdf1We investigate the influence of the structure and dynamics of the liquid outer core on the Earth's rotational modes through the squared Brunt–Väisälä frequency N2 . The frequencies of the rotational modes are embedded into the continuous spectrum of inertia-gravity modes, which is governed in the complex domain by N2 and the Earth's rotation speed. By solving the equations for the normal modes of a rotating ellipsoidal elastic earth model and varying the N2 parameter, we show interactions between pseudo-modes of the liquid core and three rotational modes: the Chandler Wobble (CW), Free Inner Core Nutation (FICN) and Free Core Nutation (FCN). The interaction between pseudo-modes of the outer core and the CW gives rise to avoided crossings, which result in two modes sharing similar displacements, that is, an almost rigid wobble of the mantle and oscillations in the outer core having roughly the same amplitude. The corresponding eigenperiods in a corotating frame of reference are separated by a few days. Avoided crossings are also the only kind of interaction that occurs between core pseudo-modes and the FICN. The coupling is stronger than for the CW, the eigenperiods being a few hundred days apart in an inertial frame of reference. The eigenfunctions are mixed in such a way that the amplitude of the nutation of the inner core is an order of magnitude bigger than the oscillations in the outer core. The FCN shows weaker interactions with the pseudo-modes of the core. However, the shift of its nutation period can reach up to 15 d. Consequently, our results show that the angular momentum approach through Liouville's equations is not sufficient to describe fully the nutational modes.